The present invention is directed a shield and a method for shielding. More particularly, the present invention is directed to a shield and a method for shielding an electronic device to prevent radio frequency energy from entering or escaping the device.
In many electronic devices, such as those used in radio transceivers, shielding is used to prevent radio frequency energy from entering or escaping the device. For example, certain electronic components must be shielded from interference caused by radio frequency energy radiation so that the performance of the device is not degraded. Also, shielding prevents radiation from escaping the device.
Metal shields have traditionally been used for shielding electronic devices, since metal is an effective barrier to radio frequency radiation. Typically, radio frequency shields are made out of sheet metal that is bent along the sides to fold down over the device. Bending the sheet metal in this manner produces gaps at the corners where the sides are folded down. These gaps are large in comparison to the radio frequency wavelengths and allow radio frequency energy to escape and enter the device. The gaps become a particular problem at higher frequencies (smaller wavelengths).
FIG. 1A illustrates an exterior view of a conventional shield 100. The shield includes a cover 105 and a frame 115. The frame 115 is typically soldered to the board supporting the electronic device and surrounds the electronic device. The cover surrounds the frame. The cover and/or frame may include holes allowing ventilation and reducing the weight of the shield. The cover includes walls 110 and 120, and the frame includes walls 140 and 150. To make the shield easier to form, a gap 130a is typically left between the walls 110 and 120 of the cover at the corner of the shield 100. A gap 130b is also left at the corner of the shield, between the walls 140 and 150 of the frame. The gaps 130a and 130b line up in the direction of the corner of the shield, forming a gap that extends from the top to the bottom of the shield.
FIGS. 1B-1E illustrate other exterior views of a conventional shield. FIG. 1B illustrates an exterior view from a corner of the shield, showing how the gaps 130a and 130b line up to form a single gap. FIG. 1C illustrates an exterior view from one side of the shield, e.g., along the length of the shield. From this view, the gap 130a in the cover and the gap 130b in the frame are visible. FIG. 1D illustrates an exemplary view from a side of the shield that intersects the side shown in FIG. 1C, along the width of the shield. In FIG. 1C, both gaps 130a and 130b are visible. FIG. 1E illustrates an exemplary view from the top of the shield, in which the top 115 of the cover joining the walls 110 and 120 of the cover is visible. The frame is not visible in this view. In this view, the gaps in the frame and cover line up to form a gap 130 at the corner of the shield.
As can be seen from FIGS. 1A, 1B, and 1E, the gaps in the frame and the cover line up in the direction extending towards the corner of the shield, forming a single gap. This gap permits RF energy to escape and enter the electronic device encased within the shield 100.
Although only one corner of the shield is illustrated in FIGS. 1A-1E for ease of explanation, there typically is a gap at each of the corners of the shield. RF energy escapes and enters the device at each of these gaps.
Instead of bending sheet metal to form a shield, the metal can be drawn. This largely eliminates the gaps at the corners of the shield. However, this method of forming a shield is more expensive. Also, this method of forming a shield usually produces a single piece shield that is soldered to the board supporting the electronic device. The shield must be unsoldered to repair the device or the board.
There is thus a need for a shield and method for shielding an electronic device from radio frequency entering or escaping in a simple, inexpensive manner.
It is an object of the present invention to provide a shield and a method for effectively shielding an electronic device from radio frequency energy entering or escaping in an inexpensive manner, with a minimal number of parts.
This and other objects are met by a shield and a method for shielding an electronic device. According to an exemplary embodiment, the shield includes a frame surrounding the electronic device. The frame has a first frame wall and a second frame wall arranged with a first gap in between that extends along the first frame wall. The first frame wall is arranged in a first plane, the second frame wall is arranged in a second plane, and the first plane intersects the second plane. The shield also includes a cover surrounding the frame. The cover has a first cover wall and a second cover wall arranged with a second gap in between that extends along the second cover wall. The arrangements of the first gap and the second gap prevent radio frequency energy from entering or escaping the electronic device.
According to one embodiment, the first cover wall is arranged in a plane substantially parallel to the first plane, and the second cover wall is arranged in a plane substantially parallel to the second plane. The first plane and the second plane may be oriented substantially perpendicular to each other.
According to exemplary embodiments, the distance that each gap extends is a small percentage of the wavelength of the radio frequency energy. According to one embodiment, the distance that each gap extends is approximately 1% of the wavelength of the radio frequency energy.
The shield may be made of metal, and the frame may be soldered to a board supporting the electronic device. The electronic device may include at least one component in a cellular telephone.